In order to optimize a vehicle room temperature using an air conditioning system, it is very important to grasp the environmental conditions within a vehicle room. In particular, it is of paramount importance to acquire information on the vehicle occupants existing within a vehicle room. For example, it is quite important to grasp the number of vehicle occupants and the physical characteristics of vehicle occupants.
By doing so, on the basis of the number of vehicle occupants and the physical characteristics of vehicle occupant, it is possible to measure a vehicle room temperature and an amount of carbon dioxide (CO2) generated within a vehicle room. An air conditioning system can be optimally controlled based on the vehicle room temperature and the amount of carbon dioxide thus measured. This makes it possible to keep the vehicle room in a pleasant state.
As a method of acquiring information on the vehicle occupants existing within a vehicle room, there is available a technique that makes use of an infrared image sensor.
According to this technique, as shown in FIG. 1, an infrared image sensor 1 is installed in a front upper region within a vehicle room. The interior of the vehicle room is imaged by the infrared image sensor 1. Infrared rays radiated from the vehicle occupants are detected through the use of the image of the vehicle room. The number, body temperature and body size of the vehicle occupants are grasped by analyzing the distribution ratio and color of the detected infrared rays.
However, the related art has a drawback in that, as shown in FIGS. 1 and 2, the horizontal and vertical imaging widths α and β of the infrared image sensor 1 is very narrow. This poses a problem in that the vehicle occupant recognition area (α×β) is quite narrow.
Due to the narrow vehicle occupant recognition area (α×β), there is a limit in the number of vehicle occupants to be recognized. Furthermore, only a limited part of the body of each of the vehicle occupants can be recognized.
For example, as shown in FIG. 2, it is possible to recognize only a part of the driver sat on a front seat and only a part of a passenger sat on a rear seat. Furthermore, the recognition area is limited to the facial parts of the vehicle occupants.
This significantly reduces the analysis accuracy of information on the vehicle occupants, thereby making it impossible to optimally control an air conditioning system. As a result, the pleasantness of a vehicle room is deteriorated.